For dressing, in a small bowl combine oregano, parsley, lemon juice, oil, garlic, and water. Brush the vegetables lightly with some of the dressing. Grill the vegetables on the rack of an uncovered grill directly over medium heat for 12 to 15 minutes or until vegetables are crisp-tender, turning occasionally.
Meanwhile, prepare the couscous according to package directions. Transfer grilled vegetables to cutting board; cool slightly and coarsely chop. Add chopped vegetables to couscous. Stir in remaining dressing. If desired, stir in nuts. Season to taste with salt and freshly ground black pepper; toss. Makes 6 to 8 servings.